1. Field of the Invention
The present invention relates to an antiglare film, a manufacturing method thereof, and a transmission type liquid crystal display. In particular, the invention relates to an antiglare film that can be provided on the surface of a window or a display such as a liquid crystal display (LCD), a CRT display, an organic electroluminescence display (ELD), a plasma display (PDP), a surface emission display (SED), and a field emission display (FED) as well as a manufacturing method thereof and an LCD using the same.
2. Description of the Related Art
In the field of displays such as liquid crystal displays, CRT displays, EL displays, and plasma displays, an antiglare film having a concave-convex structure on the surface is known to be provided on the display surface in order to prevent the decrease in visibility caused by reflection of external light on the display surface during viewing.
For example, a method for forming a concave-convex structure on the surface of an antiglare film by emboss processing and a method of forming a concave-convex structure on the surface of an antiglare film by coating a coating liquid in which particles are admixed to a material forming a binder matrix and dispersing the particles in the binder matrix are known as methods for forming an antiglare film having a concave-convex structure on the surface. In the antiglare film in which a concave-convex structure formed by such methods is provided on the surface, the external light falling on the antiglare film is scattered by the concave-convex structure of the surface, the image of external light becomes blurred, and the decrease in visibility caused by reflection of external light on the display surface can be prevented.
Accordingly, in the antiglare film in which concavities and convexities are formed on the surface by emboss processing, surface concavities and convexities can be fully controlled. Therefore, reproducibility is good. However, the problem is that where a defect or adhered foreign matter is present on the emboss roll, the defect will appear periodically with a pitch of the roll.
JP-A-6-18706 discloses antiglare films of various forms in which particles are dispersed in a binder matrix. The antiglare films using the binder matrix and particles described in JP-A-6-18706 can be manufactured by a process including fewer steps than that using the above-described embossing and, therefore, the antiglare films can be produced at a lower cost.
A variety of techniques used to obtain antiglare films using a binder matrix and particles have been disclosed. For example, JP-A-2003-260748 discloses a technique using a combination of a binder matrix resin, spherical particles, and irregular shape particles. JP-A-2004-004777 discloses a technique using a binder matrix resin and particles of a plurality of different diameters. JP-A-2003-004903 discloses a technique providing surface concavities and convexities and specifying the cross-sectional area of concavities.
JP-A-11-305010 discloses a technique using internal scattering together with surface scattering, setting the internal haze value (cloudiness) of the antiglare layer to 1%-15% and setting the surface haze value (cloudiness) to 7%-30%. JP-A-11-326608 discloses a technique using a binder resin and particles with a diameter of 0.5 μm to 5 μm, and setting the difference in refractive index between the binder resin and the particles into the 0.02 to 0.2 range. JP-A-2000-338310 discloses a technique using a binder resin and particles with a diameter of 1 μm to 5 μm, setting the difference in refractive index between the binder resin and the particles to 0.05-0.15, using an appropriate solvent, and setting the surface roughness within a predetermined range. JP-A-2000-180611 discloses using a binder resin and a plurality of types of particles and setting the difference in refractive index between the binder resin and the particles to 0.03-0.2. JP-A-11-160505 discloses a technique setting the surface haze (cloudiness) to a value equal to or greater than 3 and setting the difference between a haze value in the normal direction and a haze value in the direction at ±60° to a value equal to or less than 4.
Antiglare films of various configurations developed to attain a variety of objects have thus been disclosed. Performance of antiglare films used on the front surface of display differs between the displays. In other words, an optimum antiglare film differs depending on the resolution and object of use of the display. Therefore, antiglare films of various types corresponding to a variety of objects are needed.
Presently, antiglare films with a high contrast are required. Among them, antiglare films with a reduced content of particles in the antiglare layer that includes the particles in a binder matrix are required. However, although the contrast can be increased in the antiglare film with a small content ratio of the particles, it is often difficult to satisfy the requirements relating to antiglare ability, absence of white blurring, and also a low level of glittering.